(1) Field of the Invention
The present invention relates generally to a structure of a tiltable steering column for a vehicular steering system. The present invention particularly relates to the structure of the tiltable steering column in which a tilt angle of a tilt bracket, the tilt bracket being pivotally attached onto a vehicle body via a clamp, is set by an engagement and disengagement of a plurality of lock pins formed on a link member(s) with and from any of plurality of lock grooves formed on a lock plate, the lock plate being axially attached to the tilt bracket and the link member being pivoted in response to a pivotal movement of an operational lever.
(2) Description of the Background Art
A tiltable steering column is generally installed on a steering shaft axially attached onto a steering wheel. The tiltable steering column is tiltable in its upward and downward directions in a vicinity to an upper end of the steering wheel so that a driver of the vehicle can manually adjust a position of the steering wheel at an optimum drive position.
Various types of the tiltable steering columns have been proposed. For example, in one of the previously proposed tiltable steering columns, a toothed portion is formed on a constant arc portion with a tilt hinge of a tilt bracket as a center, the tilt bracket to which the steering wheel being axially attached via the steering shaft, and a tooth member having a toothed portion engageable with the toothed portion of the tilt bracket is axially supported on a clamp, the clamp being fixed to a vehicle body so as to enable cooperation with a lever.
In the above-described structure of the previously proposed tiltable steering column, the meshed engagement of both toothed portions permit the set angle of the tiltable steering column to be held there at. Therefore, if a weight imposed on the tilt bracket becomes increased, a possibility of defects of the toothed portions will become high. Hence, since an air bag system has been installed on the steering column, in recent years, the possibility of defects of the toothed portions will become increasingly higher due to a low rigidity of the steering column.
To cope with the above-described drawback, another structure of the tiltable steering column has been proposed which has a relatively high rigidity and can rigidly maintain the set tilt angle.
This is exemplified by a U.S. Pat. No. 3,473,405.
In the United States patent identified above, a lock plate is axially attached on the tilt bracket and is rotatable by means of an operational lever. Lock grooves are inscribed along a width direction of the tilt bracket and are extended with predetermined intervals in an elongated direction of the tilt bracket. A lock pin engageable with each lock groove is extended from an arc extended portion of a fixing portion. When the lock pin is disengaged from any one of the lock grooves by means of a lock plate pivoting with an axle engaged with a recessed portion as a center by means of an operation of the lever. Thus, the tilt bracket is enabled to pivot with respect to the fixing portion. The tilt bracket 1 is pivoted through a desired angle and the operational lever is stopped pivoting. At this time, the desired tilt angle can be set with the lock pin engaged with any other lock pin.
However, in the above-identified United States patent, each radius of curvature formed by the respective lock grooves is varied at each position of the lock grooves when the set tilt angle of the tilt bracket is varied. Therefore, it is necessary to change each shape of the lock grooves since each outer profile of the lock grooves is varied in terms of a locking performance and locking rigidities. An assembly working for each lock groove is needed in accordance with each position of the lock grooves. Therefore, a self-contained tool is needed and accordingly requires high cost. In addition, productivity thereof becomes low and cost of manufacturing the tilt bracket becomes increased. Furthermore, a special technique of working the grooves is needed to assemble the steering column.